A vulnerability exists in the Cisco Firewall Services Module (FWSM) - a
high-speed, integrated firewall module for Cisco Catalyst 6500 switches and
Cisco 7600 Series routers, that may result in a reload of the FWSM. The only
affected FWSM System Software Version is 3.2(3).

There are no known instances of intentional exploitation of this issue.
However, Cisco has observed data streams that appear to be unintentionally
triggering this vulnerability.

Common Vulnerabilities and Exposures (CVE) identifier CVE-2007-5584 has
been assigned to this vulnerability.

Cisco will release free software updates that address this
vulnerability.

The preceding example shows that the FWSM is running version 3.2(3) as
indicated by the column under "Sw" above.

Note: Recent versions of Cisco IOS will show the software version of
each module in the output from the show module command;
therefore, executing the show module <slot
number> command is not necessary.

Alternatively, the information can also be obtained directly from the
FWSM through the show version command as seen in the following example.

FWSM#show version
FWSM Firewall Version 3.2(3)

Customers who use the Cisco Adaptive Security Device Manager (ASDM) to
manage their devices can find the version of the software displayed in the
table in the login window or in the upper left corner of the ASDM window. The
version notation is similar to the following example.

A vulnerability exists in the processing of data in the control-plane
path with Layer 7 Application Inspections, that may result in a reload of the
FWSM. The vulnerability can be triggered with standard network traffic, which
is passed through the Application Layer Protocol Inspection process.

The only FWSM release affected by this vulnerability is FWSM System
Software version 3.2(3).

Cisco has provided scores for the vulnerabilities in this advisory
based on the Common Vulnerability Scoring System (CVSS). The CVSS scoring in
this Security Advisory is done in accordance with CVSS version 2.0.

CVSS is a standards-based scoring method that conveys
vulnerability severity and helps determine urgency and priority of response.

Cisco has provided a base and temporal score. Customers can
then compute environmental scores to assist in determining the impact of the
vulnerability in individual networks.

Cisco has provided an FAQ to answer additional questions
regarding CVSS at

When considering software upgrades, consult
http://www.cisco.com/go/psirt
and any subsequent advisories to determine exposure and a complete upgrade
solution.

In all cases, customers should exercise caution to be
certain the devices to be upgraded contain sufficient memory and that current
hardware and software configurations will continue to be supported properly by
the new release. If the information is not clear, contact the Cisco Technical
Assistance Center (TAC) or your contracted maintenance provider for assistance.

FWSM software version 3.2(4) contains the fixes for the vulnerability
described in this document and will be available for download during the week
beginning 7th January 2008.

Disabling the TCP normalizing function in the FWSM will mitigate this
vulnerability.

The TCP normalizer performs the following action:

For traffic that passes through the control-plane path, such as packets
that require Layer 7 inspection or management traffic, the FWSM sets the
maximum number of out-of-order packets that can be queued for a TCP connection
to two packets. The TCP normalizer is enabled by default and is not
configurable except to enable or disable.

To disable the TCP normalizing function, use the no
control-point tcp-normalizer command in global configuration mode, as
shown in the following example.

Disabling the "control-point tcp-normalizer" will prevent strict TCP
checks, such as detecting out-of-sequence segments and monitoring TCP options,
on the TCP packets received on the Control Plane for Layer 7 inspection in the
FWSM, will not be performed. The feature should be re-enabled after upgrading
to a fixed version of software.

Cisco will release free software updates that address these
vulnerabilities. Prior to deploying software, customers should consult their
maintenance provider or check the software for feature set compatibility and
known issues specific to their environment.

Customers with contracts should obtain upgraded software through their
regular update channels. For most customers, this means that upgrades should be
obtained through the Software Center on Cisco's worldwide website at
http://www.cisco.com.

Customers whose Cisco products are provided or maintained through prior
or existing agreements with third-party support organizations, such as Cisco
Partners, authorized resellers, or service providers should contact that
support organization for guidance and assistance with the appropriate course of
action in regards to this advisory.

The effectiveness of any workaround or fix is dependent on
specific customer situations, such as product mix, network topology, traffic
behavior, and organizational mission. Due to the variety of affected products
and releases, customers should consult with their service provider or support
organization to ensure any applied workaround or fix is the most appropriate
for use in the intended network before it is deployed.

Customers who purchase direct from Cisco but do not hold a Cisco
service contract, and customers who purchase through third-party vendors but
are unsuccessful in obtaining fixed software through their point of sale should
acquire upgrades by contacting the Cisco Technical Assistance Center (TAC). TAC
contacts are as follows.

+1 800 553 2447 (toll free from within North America)

+1 408 526 7209 (toll call from anywhere in the world)

e-mail: tac@cisco.com

Customers should have their product serial number available and be
prepared to give the URL of this notice as evidence of entitlement to a free
upgrade. Free upgrades for non-contract customers must be requested through the
TAC.

This issue was first discovered via internal testing at Cisco. There
are no known instances of intentional exploitation of this issue. However,
Cisco has observed data streams that appear to be unintentionally triggering
the vulnerability.

THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME. CISCO EXPECTS TO UPDATE THIS DOCUMENT AS NEW INFORMATION BECOMES AVAILABLE.

A stand-alone copy or Paraphrase of the text of this document that omits the distribution URL in the following section is an uncontrolled copy, and may lack important information or contain factual errors.

In addition to worldwide web posting, a text version of
this notice is clear-signed with the Cisco PSIRT PGP key and is posted to the
following e-mail and Usenet news recipients.

cust-security-announce@cisco.com

first-teams@first.org

bugtraq@securityfocus.com

vulnwatch@vulnwatch.org

cisco@spot.colorado.edu

cisco-nsp@puck.nether.net

full-disclosure@lists.grok.org.uk

comp.dcom.sys.cisco@newsgate.cisco.com

Future updates of this advisory, if any, will be placed on Cisco's
worldwide website, but may or may not be actively announced on mailing lists or
newsgroups. Users concerned about this problem are encouraged to check the
above URL for any updates.